net: ena: Minor cosmetic changes

A few changes for better readability and style

1. Adding / Removing newlines
2. Removing an unnecessary and confusing comment
3. Using an existing variable rather than re-checking a field

Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David Arinzon <darinzon@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>